6.4.1 distinguish between:
• Ventilation – breathing (air in and out of lungs)
• Gas Exchange – diffusion of gases. Occurs in 2 places:
• Cellular Respiration – What is it and where does it take place?
Diffusion
• Protists, sponges, cnidarians, and flatworms all obtain oxygen and get rid of carbon dioxide via diffusion with the aqueous environment in which they live.
• In all animals, the respiratory surface must be moist and thin. In many it is highly branched to provide greater surface area.
6.4.2 Need for ventilation system
• We are large so our surface area/volume ratio is not favorable for the diffusion of gases.
• Our exterior surface (skin) is not suited for the exchange of gases. Respiratory surfaces should be moist.
• A ventilation system ensures that the transfer of gases is encouraged due to concentration gradients.
6.4.4 AnatomyDraw and label
• Nasal cavity – separated from mouth by palate. Warms, filters, moistens air
• Pharynx – common passageway for respiration and digestion
• Larynx – top of trachea, contains vocal cords. Opening to larynx is glottis, protected by epiglottis
• Trachea – C shaped rings of cartilage support. Forks into 2 bronchi.
• Bronchi branch to form bronchioles
• Tips of bronchioles end in clusters of air sacs called alveoli where gas exchange occurs.
3.4.3 Alveolar structure
• The small spherical shape of alveoli provide a large surface area for gas exchange
• Single cell thickness makes it easy for gases to diffuse through alveoli wall
• Moisture allows for efficient diffusion
• Capillary bed ensures gases do not have to diffuse far to reach circulatory system
Question
• Pneumonia (excess mucus) and smoking (tar) create an extra lining inside of each of the alveoli. Describe how and why this could become life-threatening.
Ventilation
• Mammals – negative pressure breathing.
• Recall that there is an inverse relationship between pressure and volume.
• Diaphragm and intercostal muscles change the size of thoracic cavity which changes air pressure in lung. Air always flows from high pressure to low.
Inspiration
• Diaphragm contracts (moves down) and intercostal muscles raise rib cage.
• Volume of thoracic cavity increases which lowers air pressure in lungs (partial vacuum)
• Air flows from high pressure (atmosphere) to low pressure (lung) via your mouth/nasal passages trachea bronchi……